1. Field of the Invention
Embodiments of the invention relates to a flat panel display device, and more particularly, to an apparatus and a method for driving a liquid crystal display (“LCD”) device. Although embodiments of the invention are suitable for a wide scope of applications, they are particularly suitable for obtaining a rapid response speed of liquid crystal molecules, realizing an improved image quality, and obtaining a high-resolution image in an in-plane switching mode (“IPS”) liquid crystal display device.
2. Discussion of the Related Art
To overcome a narrow viewing angle generated in a twisted nematic (“TN”) mode LCD device, an in-plane switching mode LCD device has been studied and developed, which has the advantage of a wide viewing angle. In general, in an IPS mode LCD device, a common electrode and a pixel electrode are formed in parallel on the same substrate, and a liquid crystal material is controlled by a horizontal electric field formed between the common and pixel electrodes. In comparison, a viewing angle of an IPS mode LCD device is wider than that of a TN mode LCD device.
FIG. 1 is a schematic diagram illustrating an IPS model LCD device according to the related art. In FIG. 1, a substrate 10 includes a plurality of pixels in an active area A/A on which an image is displayed. In addition, a plurality of data drivers 30 and gate drivers 40 including integrated circuits (IC) chips are mounted on a tape carrier package (TCP) 20. The data drivers 30 provide video data signals to the active area A/A, and the gate drivers 40 provide scan signals for selectively driving the pixels in accordance with the video data signals. The TCP 20 includes a plurality of conductive lines. Thus, each of the data and gate drivers 30 and 40 is electrically connected to the active area A/A. The data drivers 30 are commonly positioned at the upper side of the substrate 10, and the gate drivers 40 are commonly positioned at the lateral side of the substrate 10.
As illustrated shown in the enlarged pixel structure in FIG. 1, a plurality of data lines Dm−1, Dm, and Dm+1, are commonly formed in a vertical direction, and a plurality of gate lines Gn are commonly formed in a horizontal direction crossing the data lines Dm−1, Dm, and Dm+1. To display color images corresponding to the video data signals, the pixels having red, green and blue color filters are arranged in order of red (R), green (G) and blue (B) with respect to the gate line Gn.
In addition, each of the pixels includes a pixel electrode PE and a common electrode CE on the substrate 10. The pixel electrode PE and the common electrode CE may be formed in parallel to or at an angle of about 45° to the data lines Dm−1, Dm, and Dm+1, to thereby form a horizontal electric field parallel to the substrate 10. Based on the structure of the pixel and common electrodes PE and CE, liquid crystal molecules are aligned by a rubbing process. The rubbing process is performed along the direction of the data lines Dm−1, Dm, and Dm+1, to thereby display a normally black mode of showing a black image on a screen when an electric field is not applied to the pixel electrode PE and the common electrode CE.
FIGS. 2(a) and 2(b) are schematic diagrams illustrating a movement of liquid crystal molecules in a pixel of an IPS mode LCD device according to the related art. FIG. 2(a) shows the alignment state of the liquid crystal molecules when the electric field is not formed, and FIG. 2(b) shows the alignment state of the liquid crystal molecules when the electric field is formed. As shown in FIG. 2(a), when the electric field is not applied to the pixel electrode PE and the common electrode CE, that is, PE=CE=0V, the liquid crystal molecules are maintained in the initial alignment direction. As shown in FIG. 2(b), if the electric field is formed by respectively applying voltages to the pixel electrode PE and the common electrode CE, for example, PE=7V and CE=0V, the liquid crystal molecules rotate in proportion to the level of the applied electric field at the direction of the electric field. As a result, the light transmittance is changed based on the rotation of the liquid crystal molecules, and such an alignment change of liquid crystal molecules is referred to as ‘rising’. In addition, as the electric field dissipates between the pixel electrode PE and the common electrode CE, the liquid crystal molecules are re-aligned to the initial state as shown in FIG. 2(a), and such an alignment change of liquid crystal molecules is referred to as ‘falling’.
On the rising movement of liquid crystal molecules according to the formation of electric field, the liquid crystal molecules are rapidly rotated in comparison with the level of the applied electric field. On the falling movement of liquid crystal molecules after the electric field dissipates, the liquid crystal molecules are slowly returned to the initial alignment in comparison with those on the rising movement. In particular, the rising movement of the liquid crystal molecules are moved rapidly since the liquid crystal molecules are rotated based on the electric field. In contrast, in case of the falling movement, the liquid crystal molecules are moved depending on properties of the liquid crystal and alignment layer, for example, the elastic coefficient, rotating viscosity, or aligning force. Accordingly, the falling where the liquid crystal molecules are moved slowly causes the inaccurate alignment of liquid crystal molecules when displaying the next frame, thereby deteriorating the image quality.